Measure oxygen with fingeroximeter.

Why would an enthusiastic freediver want to use an oximeter? Performance freediving is mainly about oxygen consumption. Low consumption. It can be reached through good hydrodynamics, variating speed, more relaxation, other types of breathe-up and warm-up. Sensitizing the dive response.

How will you know what works and not. Either trust advice from more experienced freedivers or experiment for your self.

Oxygen can be measured with a gaz analyzer. Most accurate would be a blood sample. Fixing measure devices on the forehead is good, earlobe measure is ok, but finger oximeter is the cheapest and often the only realistic way for laymen.

Some question the accuracy: the meters are often not built to be accurate below 70%, others mean that vasoconstriction in limbs will make the meter not show accurate results in the finger. But a good finger oximeter reacts in a consistent way and can follow you down to at least 60% with erratic numbers.

What you can do with an oximeter is to compare results with yourself after changing different factors: diet, warm-up, breath-up, movements, relaxation. If you do the same breathhold time many times making sure only changing one factor at the time, you will be able to draw some conclusions. But you will have to do the same thing many times. You dont have to follow the measurement down to blackout levels at 50%, you will be able to draw conclusions on the rate of your consumption, compare with onset on contractions and heart rate

Questions that a oximeter will be able to answer:

- Are you sqeezed? A finger oximeter will directly show that your Sp02 recovery is slow. Some divers come up and within a minute levels are restored, other come up and linger just above 90% for hours (=squeeze).

- Which breath up is most efficient?

- How does warm up affect the 02 values at the end of a breath hold?

- If your oximeter is accurate down to 70% you can try to maximize you breathhold times down to that level, and thus find the best warm-up/preparation.

- Finger oximeters give their lowest result after about 25 seconds after termination of apnea.
- Earlobe oximeter give their lowest result about 5 seconds after finish.
- The only true values of O2 you get from bloodgas samples (draw blood).
- Finger oximeters are known to (at the end of breathhold) show higher values than earlobe meters.

A too cheap oximeter might not do it for you. The oximeter in the picture is an example of a finger oximeter used by scientist for simpler test. The meter above can also be found here - or here.

Here are a few other examples.